1. Field of the Invention
The present invention relates to a technology for combining real time communications which processes multimedia data, etc., with non-real time communications which processes other data, and controlling the combination in a network such as a packet network, etc., and more particularly to a technology for effectively performing non-real time communications in which a bandwidth is restricted, on a network where resources are reserved with higher priority for real time communications and where its bandwidth is to be secured.
2. Description of the Related Art
When multimedia applications for performing communications of multimedia data such as audio data and video data are used on a network such as a packet network, etc., and when the transfer of these data are delayed due to heavy traffic on the network, users feel disturbed, since the continuity of sound and pictures is interrupted. To prevent this situation it is important that the bandwidth of real time communications is guaranteed on a network for processing multimedia data.
Conventionally, a technology is known to guarantee the bandwidth of the real time communications for preferentially assigning network resources to the real time communications for processing multimedia data, etc., by restricting the use of the network resources by the non-real time communications.
In fact, the bandwidth determined by subtracting the bandwidth assigned for the real time communications from that assigned for the whole network is assigned to each node apparatus. Each node apparatus restricts the bandwidth of the non-real time communications in such a way this bandwidth does not exceed the bandwidth which is assigned to each node apparatus.
However, the above-described prior art is not originally provided with a means for estimating necessary bandwidth based on the current used status of the non-real time communications and for updating the bandwidth limit value of the non-real time communications of each node apparatus according to the current used status. As a result, in the above-described prior art, since the non-real time communications cannot use the network resources effectively, a status occurs in which the delay of transfer of the non-real time communications increases, etc., which makes users feel disturbed when the used status of the non-real time communications by users changes. This is a problem of the prior art.
Although a method for deciding the assignment of the network resources based on its used result by observing the used status of the non-real time communications over a long period of time, is considered to be a method for estimating necessary bandwidth based on the current used status of the non-real time communications, this method has the problem that the network resources cannot be effectively assigned when the non-real time communications having strong data burst characteristics, occur.
Even if a means by which the occurrences of the non-real time communications having strong data burst characteristics are detected and even if the reassignment of the bandwidth of the non-real time communications can be requested based on it, a heavy traffic is caused on the network when the bandwidth of the non-real time communications is reassigned to all the node apparatuses at the time of the occurrence of the request for its reassignment. This increases the load of each node apparatus composing the network and causes the functioning of the network to deteriorate. This is another problem of the prior art.